Ultrasound imaging is generally used by doctors to inspect tissues within a human body. A doctor may place the probe on the surface of the skin above the target tissues, after which ultrasound images of the tissue may be obtained. Due to its safety, convenience, non-invasiveness and low cost, ultrasound imaging has become one of the primary tools to aid in medical diagnoses. Obstetrics is one of the fields in which ultrasound imaging is most widely used. With the use of ultrasound, the effects of X-rays and the like on the mother and the fetus may be avoided making it superior to other imaging modalities. With ultrasound imaging, not only may observation and measurement of the fetus in morphology be conducted, but also information about physiology and pathology, such as respiratory and urinary information, may be obtained, thereby evaluating the health and growth status of the fetus.
When inspecting the nervous system of the fetus, the corpus callosum and the cerebellar vermis are two very important inspection targets. The corpus callosum is the largest conjugate fiber between the hemispheres of the brain, and is responsible for the communication between the cerebral hemispheres. Deficiency or hypogenesis of the corpus callosum will lead to several complications, such as epilepsy, mental retardation or dyskinesia. Deficiency or hypogenesis of the cerebellar vermis is a symptom of Dandy-Walker syndrome. Fifty percent of patients with the Dandy-Walker syndrome show signs mental retardation and usually have chromosome abnormalities and other deformities with poor prognoses and high mortality rates. Accordingly, the abnormalities of the corpus callosum and the cerebellar vermis represent critical diseases. If they are not found during the prenatal examination, they could bring huge mental and economic burdens to the family of the patient and the society. However, the corpus callosum and the cerebellar vermis are very easy to be misdiagnosed or missed during the inspection of the nervous system of the fetus. The reason is that it is very difficult to obtain the median sagittal section image of the fetus, which is the best image for observing the corpus callosum and the cerebellar vermis, by a conventional two-dimensional ultrasound imaging due to the affects of the factors such as fetal position, amniotic fluid, obstruction of the nasal bone, and skill of the doctors, etc. Even if the image of the median sagittal section can be obtained, doing so may take a long time. Accordingly, many doctors have to indirectly inspect the corpus callosum and the cerebellar vermis by images of other sections (such as the cerebellum section or the thalamus section, etc.), increasing the risk of misdiagnosis.
Recently, with the widespread use of the three-dimensional ultrasound imaging, some doctors perform a three-dimensional scanning on the fetus starting from the biparietal diameter section, obtain an image of the median sagittal section of the fetus by geometric transforms of 3D ultrasound image data, such as manual rotation and translation, and then inspect the corpus callosum and the cerebellar vermis through this median sagittal section image. Although the median sagittal section image obtained by this method may have relatively lower quality than a conventional two-dimensional image, the corpus callosum and the cerebellar vermis can be relatively clearly displayed, and abnormalities of the corpus callosum and the cerebellar vermis can be determined quickly and precisely. In order to image the median sagittal section in three-dimensional space by manual rotation and translation, the doctors must understand the three-dimensional space very well. However, most doctors have no science and engineering background and lack the requisite understanding of three-dimensional space. Therefore it is very difficult for doctors to obtain the median sagittal section image from volume data.